Amazon has a great deal on the Werner 16′ Multi-Master ladder: $164.00 with free super saver shipping.
The Multimaster is a 16′ ladder that has multiple functions (from the Werner website): double stepladder, stepladder, stairwell ladder, multi-shelf, stand-off ladder, fully extended straight ladder, 1/2 & 3/4 length straight ladder, self-supporting scaffold, extended span scaffold, stairwell scaffold.
Basically it has four jointed locking sections that can allow it to be used as a straight ladder, a stepladder, or scaffolding. The other functions are related to the adjustability in height and angle. Marketing hype aside, it does seem to be a versatile product and may well be the only ladder you need for the majority of tasks inside and out. It has a 250 lb. load capacity (which means that several of our contractor friends would be overloading it…)